1. Field of the Invention
The present invention relates to a liquid ejecting apparatus which ejects a droplet of a liquid from a nozzle.
2. Description of Related Art
An inkjet recording apparatus disclosed in JP-A-2005-288770 includes an inkjet recording head and a sub tank storing ink to be supplied to the recording head. The sub tank is vertically divided by a gas- or air-permeable film into two parts. The lower part, that is, the part located under the air-permeable film, constitutes an ink chamber for storing the ink, and the upper part, that is, the part located over the air-permeable film, constitutes a gas or air chamber to which a gas or air is discharged from the ink chamber. With the air chamber, a suction pump is connected through a valve opened and closed by a controller. To discharge the air from the air chamber and the ink chamber to the external, the suction pump is operated with the valve held opened so as to suck the air from the air chamber. After sucking the air from the air chamber by the suction pump, the valve is closed to hold the internal pressure of the air chamber at a lower level. A gas or air flowing into the ink chamber thereafter is sucked and discharged to the air chamber by the lowered pressure in the air chamber. Thus, it is prevented that when the ink is supplied to the recording head from the ink chamber, the gas or air flows into the recording head along with the ink. This inkjet recording apparatus further includes an ink suction cap that covers the recording head and sucks ink of which the viscosity has been increased, and others, from the inside of the recording head through nozzles formed in the recording head. a liquid
In the above-described inkjet recording apparatus, the present applicant examined use of a single suction pump that is selectively connected to one of the air chamber and an ink suction cap so that the suction pump can function as a suction pump as well as a pump for the ink suction cap that operates to suck the ink from the nozzles.
Further, the applicant examined employment of a differential pressure valve that opens and closes without being controlled by a controller and in accordance with a pressure difference between a downstream space and an upstream space, so as to reduce the cost incurred by using a valve that requires a controller for its operation.
As a result of the examinations, applicant has found that when the above-described two techniques are employed, the ink sucked from the recording head adheres to a portion where connection of the suction pump is switched between the air chamber and the ink suction cap, and the adhering ink may separate therefrom and flow to the differential pressure valve disposed between the air chamber and the suction pump. When the ink reaches the differential pressure valve and adheres thereto and the viscosity of the ink increases there, the differential pressure valve become unable to normally operate.